Control system



Oct. 3, 1944. A. E. KROGH 2,359,651

CONTROL SYSTEM Filed Jan. 16, 1942 2 Sheets-Sheet 1 FIG.|.

INVENTOR. ANKER E. KROGH A ORNEY Oct. 3, 1944. v A. E. K-ROGH 2,359,651

CONTROL SYSTEM Filed Jan. 16, 1942 2 Shets-Sheet 2 INVENTOR. AN KER E. KROGH OR'NEY Patented Oct. 3, 1944 CONTROL SYSTEM Anker E. Krogh, Mount Airy, Pa., assirnor to The Brown Instrument Company, Philadelphia, Pa., a-corporation of Pennsylvania Application January 16,1942, Serial No. 427,028

6 Claims.

The general object of the present invention is to provide improved apparatus for use in cooking size supplied to cotton and rayon slashing machines of textile mills. More specifically stated, the general object of the invention is to provide improved apparatus for automatically controlling the temperature of the size during the cooking operation, and the duration of that operation, and for automatically maintaining the cooked size at a predetermined temperature lower than the cooking temperature during a variable period in which the cooked size is held in storage in the vessel in which it has been cooked. The use of the cooking vessel as a storage receptacle for cooked size, saves the cost of special storage provisions, saves in plant floor space, and saves heat otherwise lost when cooked'starch is transferred from the cooker to a separate storage receptacle. g

In a simple and desirable form of the present invention, I employ an air operated recording thermometer which includes remote index setting provisions and which is of known commercial type, to close and open a valve supplying the steam used in heating the size cooking vessel in automatic response to the temperature of the size as the latter rises above and returns to the predetermined cooking temperature. The steam valve thus opened and closed by the thermometer may well be a diaphragm valve of commercial typ comprising a motor or diaphragm chamber to which the thermometer aircontrol provisions supply air under pressure to open the valve, and alternatively permit air to escape from said chamber to close the valve.

With the above described thermometer and steam supply valve, I combine a cooking; timer,

which may well be of known type, and which opdisc chart of the recording thermometer.

erates to terminate the cooking operation at the end of a predetermined cooking time which may be varied by the adjustment of the timer. The

timer thus terminates the cooking period by oper-;

ating through the remote index setting provisions to so adjust the control thermometer that the latter will thereafter operate to mainain a suitable size storage temperature of 170 or so, in stead of the previously maintained size cooking temperature of 208 or so. In the preferred practical form of the invention, the timer energizes a venting solenoid valve of commercial type,

which, when energized, closes" communication between the air control provisions of the thermometer and the diaphragm chamber of the steam supply valve, and opens the last mentioned chamber' to the atmosphere. advantageously, the

above described apparatus includes simple push button or analogous control means for initiating which may be of relatively simple and inexpensive commercial types. A record of the size temperature variations occurring during a plurality of successive cooking operations during a single 24 hour day, may be recorded on a single 24 hour The simple on and oil control of the steam supply to the size cooker permits of a suitably close control of the size temperature during the cooking operation, in consequence of the very considerable heat storage capacity of the size cooker and the size therein. The automatic control of the size cooking temperature, and of the cooking period duration, eliminates boiling-over," insures desirably uniform starch solutions, eliminates risk of undercooking or overcooking the starch, and avoids waste of steam in the size cooking operation. Moreover, the required control instrumentalities are relatively simple in operation, easy to adjust and easy to maintain in operative condition.

In cooking thick boiling starch, it is necessary, or at least desirable, to bring the starch up to a temperature of or so, which is somewhat below the full cooking temperature, during an initial period of the cooking operation, and to then maintain the starch-temperature without material change during a period of fifteen minutes or so to permit the beneflcent action of enzymes. This interruption in the rise of the size temperature may be effected in accordance with the present invention by adding to the sim- The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification.- For a better understanding the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have diagrammatically illustrated and described. various embodiments of my invention.

Of the drawings:

Fig. 1 is a diagrammatic aepresentation of a, simple form of the invention.

Fi 2 is a sectional elevation of a control valve shown in Fig. 1 and Fig. 3 is a diagrammatic representation of a form of the invention including means for temporarily interrupting the rise in the size temperature during an early stage of the cooking operation.

In the simple form of the invention shown diagrammatically in Fig. 1, the size is cooked in a cooker or cooking vessel A, of conventional type, which is heated by steam supplied by a pipe B at a rate determined by the adjustment of an automatic control valve C. The latter is adjusted during the cooking operation as required to maintain a suitable predetermined cooking temperature, which may be about 208 F., by a control instrument D which cooperates with a thermometer bulb E in the cooker A to continually meas me and record the size temperature. Advantageously, and as shown, the instrument D is a recording thermometer of well known commercial type which includes air control provisions for effecting an on and off control 01' the valve C. In the form of the invention shown in Fig. 1, the cooking operation proper, is terminated after a cooking period of predetermined extent by a cooking timer F, which includes a timing motor F, a timing switch J, and cooperating parts hereinafter described.

As diagrammatically shown in Fig. 1, the steam supply valve is opened to initiate the cooking operation and the timer F is started into operation by the closure of a push button switch G. At the termination of the cooking period, the timer F, which operates continuously during the cooking operation, terminates its own operation and at the same time adjusts the control instrument D, so that the latter will then operate to maintain the. lower storage temperature of 170 or so. A second push button switch H is mechanically interlocked by a lever HG with the starting switch G so that the closure of either opens the other.

The switch is actuated at the conclusion of each cooking operation to close the valve C and to reset the timing mechanism F in a manner hereinafter described, preparatory to the initiation of a subsequent size cooking operation.

The essential elements of the thermometer D are diagrammatically illustrated in Fig. 1. As there shown, those elements comprise a spiral Bourdon tube K, to the stationary end K or which a pressure proportional to the temperature of the size in thecooker A, is transmitted from the thermometer bulb E through a pipe or capillary tube K". The movable end K of the Bourdon tube K is connected to an arm K which oscillates about the axis oi the spiral as the temperature in the bulb E varies. A link K connected at one end to the arm K at apoint adjustable along the length of the latter, has its other end connected to a lever L which is secured to, and gives angular motion to a pen shaft L which carries the recording pen arm 1.. of the instrument D. Y

The air control provisions of the instrument D as diagrammatically shown in Fig. 1, comprises a flapper or valve N pivoted at N, and adjusted by the oscillation of a lever M pivoted at M, toward and away from a position in which it en gages and closes the vent orifice of a bleed nozzle O. The flapper N is biased for movement into engagement with the nozzle 0 and the lever M includes a flapper lifter pin M which engages the flapper and moves' it way from the nozzle 0 when the lever M is turned clockwise.

The means shown in Fig. l for angularly adjusting the valve M as the size temperature varies, comprises a link M having its lower end connected to lever M and having its upper end connected by the pivot M to a lever M at a point intermediate the ends of the latter. One end of the lever M is suspended by a link M from one end of the lever L. The second end of the lever M is connected through a pivot P to a control point adjusting lever P supported by a pivot P and carrying the usual control point index arm P As shown, the lever P is connected by a link X to an actuating lever arm X" of a remote index adjusting device X which operates to vary the angularposition of the lever P and thereby vary the position oi the index arm P and the elevation 01 the pivot P. As will be apparent, the effect or raising or lowering the pivot P is to respectively increase or decrease the size temperature required to eifect sumcient counterclockwise movement of the arm K to cause movement of the flapper N away from the nozzle As shown in Fig. 1 air under pressure is supplied to the nozzle 0 by a supply pipe Q, including a pressure regulating valve Q, adjusted to maintain a suitable and approximately constant air pressure at the inlet side of a restricted oriflce Q interposed in the supply pipe Q between the pressure regulator Q and the nozzle 0. The pressure at the outlet or the regulator Q is indicated by a pressure gauge Q The nozzle pressure of the outlet side 01 the oriflce Q is transmitted by pipe or conduit Q to a booster valve Q which reduces the pressure of air received through the pipe Q from a portion of the supply pipe Q between the regulator Q and the restricted orifice Q as required to maintain a control pressure in its outlet pipe Q which is proportional to the nozzle pressure in the pipe Q. The booster valve Q is advantageously of the Well known commercial type used in Brown air controllers and one form of which is disclosed in the Moore Patent 2,125,081 and hence need not be further described or illustrated herein. The control pressure transmitted through the pipe Q is indicated by a pressure gauge Q.

Whether the diaphragm chamber C of the which are connected by a port R.

Q" or to the atmosphere, depends upon whether the solenoid coil R of a venting solenoid valve R is or is not energized. The valve R may well be of a commercial type. In the form shown by way of illustration in Fig. 2. it comprises a valve casing enclosing valve inlet and outlet chambers The valve casing is also formed with a port R. forming a vent from the outlet chamber of the valve, above and co-axial with the port R. A vertically movable valve member R is biased for down movement into the position in which it closes the-port R and opens the vent port R, and thereby prevents the transmission of the control pressure in pipe Q to the diaphragm chamber C, and opens the latter to the atmosphere. The valve C is member F is energized and the arm F drops back biased to close when the pressure in the chamber C is reduced to or below the pressure maintained in the pipe Q when the nozzle is not throttled by the flapper N.

As diagrammatically shown, the valve member R has its stem extending upwardly through the vent port R and connected to the lower end of an armature core R axially disposed in the solenoid coil R The energization of the latter, effected as hereinafter described, raises the valve member R to the position in which it closes the vent port R and opens the port R, and thus permits the control pressure to be transmitted through the inlet and outlet chambersof valve R,

and through the pipe Q to the diaphragm chamber C, so that valve C will open if the size tern the flapper perature is then low enough-to permit M to throttle the bleed nozzle 0.

The timer F may be of any one of various known types. As diagrammatically illustrated by way of example in Fig. 1, the timer F comprises,"

shown. A switch actuating arm F is normally clutched to the shaft F for counterclockwise movement by the motor F between an initial position shown in full lines and a dotted line switch actuating position. In its initial full line position, the arm F engages a stop pin F adjustably secured in a slot F extending circularly about the shaft F. The adjustment of the pin F along the slot F varies the duration of the cooking operation by varying the angular distance between the full line and dotted line positions of the arm F The arm K may be unclutched from the shaft F by the energization of an electromagnet F. The latter is energized, as hereinafter described, after the arm I? has been moved into its dotted line position, and the arm 1? is then free to fall back into the full line position under action of gravity, and thus reset the timer preparatory to a subsequent cooking operation, r;

During the final portion of the movement of the arm F into its dotted line position, it actuates the timer switch member f. As diagrammatically shown, the switch member F is L shaped comprising an uprising arm connected at its upper end to and suspended from a, pivot j, and comprising a second arm extending horizontally away from one side of the lower end of the uprising arm. Adjacent its free end, the horizontal arm carries at its under side bridging contact member 1 The switch member f is adjusted between its full and dotted line positions shown in Fig. 1 by actuating means comprising a bell crank lever f journaled on the pivot j and having an uprising arm to the upper end of which one end of a snap action spring f is connected to the switch member at a point some distance below the pivot pin As the bell crank is oscillated between its full and dotted line positions shown in Fig. 1, the line of action of the spring passes from one side to the other of the axis of the pivot. In consequence the spring I holds the switch member in its full line, closed position when the lever f is in its full line position, and when the lever is in dotted line position, the spring i holds the switch member I in its dotted line, open position.

As the arm F approaches its dotted line position, it engages the horizontal arm of the bell crank f and moves the latter from its full line into its dotted line position, and thus adjusts the switch member I into its open position. When into its full line position, the bell crank f returns under the action of gravity or other biasing force to its full line position, and thus returns the switch member f to its full line, closed position. The remote index setting device X through which the timer F adjusts the instrument D to terminate the cooking operation and to initiate the hot storage operation comprises a casing X enclosing a chamber X which is closed except for a central opening in its upper end wall. A bellows element X is located in the casing)! and has a closed and movable lower end, and has its upper end open-and connected to the top wall of the casing X, at the margin of the central opening therein. During the cooking operation, the space the chamber X external to bellows X is coniiected 'to theair supply pipe Q at the outlet side 7 of the'pressure regulator Q by a branch pipe Q.

Thepressure in the chamber X contracts the bellows-X until the force exerted by said presan electric motor F, adapted to slowly rotate a 1 shaft F through speed reducing gearing not.

sure isneutralized by resiliency of the bellows and 'ofa spring X which acts between the bottom end wallcfthebel lo'ws' X and the upper portion of the casing X. p

The bottom wallof the bellows X is connected by a red X to an arm X secured to a rock shaft.

X" journaled in an upper end portion of the casing X. A second arm X normally secured to and turning with the shaft X",and angularly which may be, and as shown is, identical with the valve R, and which has its solenoid winding R included in the energizing circuit of the timer F, In consequence, the size cooking temperature which the instrument D maintains depends upon the mechanical linkage, including the parts X X X", X and X between the control point adjusting lever P and the bottom wall of the bellows X and may be varied by varying the effective length of that linkage. At the end of the cooking period the timer F deenergizes the valve RA, but not the valve R. On the de-energization of the valve RA, the chamber X is opened to the atmosphere by the valve and the bellows X expands. This gives a clockwise adjustment to the lever P and the instrument DA then tends to thereafter the electro-magnetic clutch releasing maintain a storage size temperature lower than the previous size cooking temperature. That storage temperature depends upon the effective length of the linkage between the lever P and the bottom wall of the expanded bellows X and may be adjusted by varying the effective length of said linkage.

With the timer F of Fig. 1 in the condition push button Galso energizes both the solenoid R of the valve RA and the timing motor F and .starts the latter into operation. Current for thus energizing the solenoid R and the motor F is supplied by supply conductors l and 2.

On the closure of the switch G, a branch conductor 3 from the supply conductor I is connected by said switch and a conductor 4 to one terminal of the winding R. 01 valve R. The secnd terminal of that winding is connected by return wiring I to the supply conductor 2. On the closure of the switch G, th conductor I is also connected through conductor 4 to one terminal of the motor F. The second terminal of motor F is connected by a conductor I, the bridging contact f or the switch I and a conductor I to one terminal of an indicating device J, which may be a signal lamp, and which hasits other terminal connected bya conductor I to one terminal of the solenoid winding R of the valve RA. The second terminal of that winding is connected by a conductor I to the supply conductor 2.

During each cooking operation of th apparatus shown in Fig. 1, the solenoids R and R are thus continuously energized and eachv or the valves R and RA is continuously open. The control pressure then transmitted from the instrument D to the chamber C of the valve C through the pipe Q", valve R and pipe Q' keeps the valve 0 wide open when the size temperature does not exceed the predetermined cooking temperature. When the size temperature exceeds said predetermined temperature, the instrument D reduces the pressure in the chamber C, and thereby permits the valve C to close.

After the cooking operation has continued for the predetermined time fixed by the adjustment of the stop pin F in the slot F", the arm 1" of the cooking timer F engages, the switch actuating lever f and turns the latter irom its full line position into its dotted line position. This change in position of the lever f moves the snap action spring transversely across the axis of the pivot and snaps the switch member I into its open position. This moves the bridging contact I" out oi engagement with the switch contacts to which the conductors 4 and I5 are connected and thereby de-energizes the motor F, the device J, and

the winding R of the venting solenoid valve RA. 1

Thi permits the valve member R oi the valve RA to move downward and close thevalve port R while opening the port R. and thereby the chamber X to the atmosphere, whereupon the bellows X expands and operates through lever X and link X to reduce the size temperature which the instrument D tends to maintain from the cooking temperature of 208 or so, to the storage temperature of 170 or so. This immediately closes the steam valve C and terminates the size cooking operation initiated when the switch G of Fig. l was last previously closed. Following the closure of the valve C, the size slowly cools, as a result of radiation and other heat losses, until the size temperature is lower than the predetermined storage temperature, whereupon the instrument D opens the steam valve C and thereafter said instrument D closes and opens said valve as required to maintain the size at approximately the predetermined storage temperature.

The closure of the push button switch member H closes the energizing circuit 01 the element I" which permits the arm F to return to its full line position and thus rests the timer F for a subsequent size cooking operation. The energizing circuit closed by the switch H comprises the branch 9 of supply-conductor I, the electro-magnetic resetting device F, a conductor ll,'an indicator I, which may be a signal light, and the return wiring 8 connected to the supply conductor 2. The closure of the switch H thus not only re- 76 assaam sets the timer F of Fig. l, but also energizes the indicator 1, which then indicates that the. apparatus is in condition to begin cooking-a fresh batch of cool size, which may be placed in the cooker A alter the removal of the previously cooked charge, I

As previously stated, incooking thick boiling starch, it is necessary, or at least desirable, in heating up the starch to arrest the temperature ri e for fifteen minute or so, on the attainment 01' a size temperature 01' about It, to give time for enzymes to work on the starch. At the end of that period the temperature 01' the starch should be raised to mil cooking temperature, which ordinarily is about 208 F.

In Fig. 3 I have diagrammatically illustrated how the apparatus shown in Figs. 1 and 2 may be used in comunction with a second, or delayed rise timer FA, an electro-magnetic switch 8, A second and very simple thermoinetric device '1, and a second thermometer bulb TE, to maintain the size at the enzyme action. temperature of 180 F. or so, for a suitabl period. As diagrammatically shown in Fig, 3, the delayed rise timer FA may be a duplicate oi the timer F shown in Fig. 1, except that ordinarily the reducing gear (not shown) between the motor F and the switch actuator arm l" or the timer FA should be arranged to give a more rapid angular movement to the arm 1' of the timer FA than is given to the arm F of the timer F.

As hereinafter explained, the timer FA and electro-magnetic switch 8 are bothenergized by the thermometric device T, which may well be 01' simple commercial type commonly, called a "blind temperature controller, as it need include no temperature exhibiting provisions. As diagrammatically shown in Fig. 3, the device '1 comprises a snap action switch t and a bellows element T, which is contracted to close the switch t by pressure transmitted by the thermometer bulb TE, when the size heats up to the enzyme action temperature. Said pressure is transmitted from the bulb TE through a pipe TE to the chamber '1 inthe casing body T o! the device T. The bellows T is located within the chamber '1 and has a closed vertically movable, lower end, and has its upper end open and secured to the annular top wall of the casing '1 surrounding a cen tral opening in said wall. The contraction oi the bellows T by the pressure in the chamber '1 is opposed and regulated by a spring '1",

- A bellows rod or strut '1' acts between the lower end otthe bellows T' and a bell crank lever t journaled on a horizontal pivot t carried by the casing T The switch t is similar inshape to the previously described switch 1, and is Journaled on the pivot t, and is connected to the lever t by a spring 9. The latter is moved past the axis of the pivot t as the size heats up to the enzyme action temperature oi' 180 or so, with the result that the switch t is then given a closing adjustment. While the parts t and t are similar in shape and in their coaction to the previously described timer switch parts I and I, the vertical portions of the parts t and t extend upwardly and downwardly, respectively, from the pivot 13', and the horizontal arm oi the switch t carries a bridging contact t at its upper side, so that it is moved upward on the closing adjustment of the switch t.

The closing adjustment of the switch 1. energizes the timing motor F of the delayed rise timer FA, and energizes the electro-magnetic switch S and thereby deenergizes the motor F of the timer F, and temporarily terminates the control of the steam supply valve C by the instrument D by deenergizing the coil R of the valve R. When the motor F of the timer EA acts through its arm F to open the associated switch 1, the motor and the electro-magnetic switch S are each deenergized. The deenergization of switch S permits the solenoid coil R of the valve R to be reenergized and thereby again subjects the steam supply valve to control by the instrument D. The timer FA, solenoid coil R switch S and device T are operatively connected by electric circuit connections, for coaction as described.

Those connections comprise a branch conductor l3 from the supply conductor I, connected by the bridging contact f" of the timer FA to a conductor l4 when said bridging contact is in its closed position. The conductor I 4 extends to one energizing terminal of the motor F of the timer FA. The other terminal of said motor is connected by a conductor I5 to one terminal of the winding of the electro-magnetic switch S. The latter has its second terminal connected by a conductor Hi to one of the two stationary contacts engaged by the bridging contact t of the device T when the last mentioned contact is adjusted into its closed position. The other of said stationary contacts is connected by a conductor I1 and conductor 8 to the supply conductor 2.

The energization of the electro-magnetic switch S breaks th connection between the conductors 1A and 1B established by the switch S when the latter is deenergized. In Fig. 3-the conductors 1A and 1B and switch S replace the conductor 4 of Fig. 1, in the energizing circuit of the solenoid coil R of valve R. In consequence, the energization of the switch S closes the valve R and thus interrupts the supply of steam to the cooker A. In Fig. 3, the electro-magnetic resetting device F of the timer FA is connected in series with the device F of the timer F, and with the signal light I, the conductor I 2 connecting the light I to one terminal of the device F 01' timer FA, and the second tenninal of that device being connected by a conductor MA to supply conductor 2. t

In Fig. 3 the energization of the valve R is controlled jointly by the push button switch G and electro-magnetic switch S, and is independent of the operation of the timer F though subject to de-energization for enzyme action purpose through the switch S by the timer FA. In Fig. 3, the timer F directly terminates the cooking period, but does this by de-energizing the I venting solenoid valve RA, which has its solenoid winding connected in an energizing circuit including the conductor 6 which extends from the timing switch of the timer F to one terminal of the signal light J, the conductor 18 which connects the second terminal of the signal light J to one terminal of the winding of the valve RA, and a conductor 19 which connects the second terminal of said winding to conductor HA and thereby to the supply conductor 2. In the contemplated use of the apparatus shown in Fig. 3, a cooking operation is initiated by closing the switch G. This energizes the motor of the timing device F, and the windings of the valves R and RA, and thereby opens each of those valves. With the low size temperature then prevailing, th full air pressure will be transmitted from the instrument D to the chamber C of the valve C, and the latter will then be in its wide open position.

When thereafter the size temperature builds up to its predetermined enzyme action temperature of 180 or so, the switch t of the device T is actuated to connect the'conductors l6 and I1, and thus energizes the electro-magnetic switch S and the timing motor F of the timing device FA. The energization of the switch S disconnects the conductors 1A and 'IB and thereby deenergizes the timing motor F or the timing device F and deenergizes and closes each of the electro-magnetic valves R and RA. When the operation of the timing motor F of device F is thus interrupted, its switch actuating lever F will occupy a position intermediate its starting and switch actuating positions. The closure of the valve R closes fuel valve C and cuts oil the supply of fuel to the cooker, and thus the closure of the valve RA, when the switch S is energized, is without functional significance.

The interruption of the heat supply to the cooker, eflected by the energization of the switch S, continues for a suitable enzym action period of 15 minutes or so, required for the timer FA to open its switch I and thu open the energizing circuit for the switch S and motor F of the timer FA. The resultant deenergization of the switch S reconnects the conductors IA and 1B and thereby reenergizes the timer F and the windings R and R of valves R and RA, and both of those valves remain open thereafter until the size cooking operation is terminated by the timer F when its arm F reaches its switch actuating position and opens the energizing circuit for the timer F and solenoid R of valv RA.

Ordinarily, there will be a considerable time interval between the initial attainment by the size of its full cooking temperature and the termination of the cooking operation by the timer F, and during that interval the air control provisions of the instrument D will open and close the fuel valve C as required to prevent the size temperature from varying significantly in either direction from the predetermined full cooking temperatures.

While the deenergization of the energizing circuit of the timer F at the end of the cooking operation closes the valve RA, it leaves the valve R open and so long as the switch G remain closed, the air control provisions of the instrument D open and close the valve C as required to maintain the size at the storage temperature of 170 or so, as in the arrangement shown in Fig. 1.

While in Fi 3 the timer F directly terminates the cooking operation, the duration of the cooking period is determined jointly by the timers F and FA, and is equal to the sum of the time periods required for the movements of the arms F of the two timers F and FA from their respective initial positions to their respective switch actuating positions.

It is theoretically possible, of course, to use a single timer of the known type including a. time program cam and associated switch means, to do what is done collectively by the timers F and FA of Fig. 3.. However; the use or the two timers F and FA has the practical advantage that those timers which may be duplicates of one another, may be a very simple and easily adjustable type so that the timing action of each may be varied quickly and easily as conditionsmade desirable.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. The combination with a size cooker and hot storage device comprising a size chamber, of an air actuated valve regulating the supply of heat to the chamber, a thermometer responsive to the temperature of the size' in said chamber and including air control means normally operative to close and open said valve as the size temperature rises above and falls below a predetermined cooking temperature, and timing means operating after a cooking period of predetermined duration to adjust said thermometer into a condition in which it is operative to close and open said valve .as the size temperature rises above and falls beperiod to maintain the size at a predetermined temperature of the size in the chamber and including an air control means normally o erative to close and open said valve as size temperature rises above and falls below a predetermined temperature, adjusting means in said thermometer operative to adjust the temperature at which said size is maintained to a diilerent predetermined point, and timing means operated after a cooking period oi predetermined duration to operate said adjusting means to lower the temperature at which said size will be maintained and thereby initiate a hot stora e period of indefinite duration, and means operable independently of said heating means to interrupt the supply ofheat to said chamber and thereby terminate such hot storage period, and to simultaneously reset said timing means preparatory to the initiation of a subsequent cooking period.

3. The combination with asize cooker. or a regulator controlling the supply of heat to the cooker, thermometric means responsive to the temperature of the size in the cooker and norm ally controllin said regulator and adjusting the latter as required to maintain a predetermined size cooking temperature, other thermometric means responsive to the temperature of the size in the cooker and operated on the attainment of a predetermined size temperature lower than the said cooking temperature to interrupt the control of said regulator by the first mentioned means and to adjust said regulator to cut oil the supply of heat to the cooker, timing means restoring the control of the first mentioned thermometric means over the regulator at the end of a predetermined period following said temperature 'attainment and terminating the cooking operation after a predetermined duration thereof, and means forming part of said first thermometric means operative upon completion of the cooking lower temperature.

4. The combination with a size cooker, of an air actuated valve regulating the supply of heat to the cooker, a thermometer having an adjustable control point responsive to the temperature 01 the size in said cooker and including an air control means normally operative to close and open said valve as the size temperature rises above and falls below a predetermined temperature, a timing device, means for starting said device into operation at the beginning of a cooking operation, means'actuated by said device after a predetermined extent ofoperation of the latter to adjust the control pointof the thermometer to a storage temperature lower than said predetermined temperature, means responsive to the temperature of the size in the cooker and actuated on an attainment of a predetermined temperature lower than the first mentioned temperatureto interrupt the operation oi said timing device for a predetermined period of time and to simultaneously render said thermometer inoperative to open said valve and to eflect the closure of the latter for an interval shorter than the period oi. operation of said timing device.

5. The combination with a size cooker, of an air actuated valve regulating the supply or heat to the cooker, a thermometer responsive to the temperature of the size in said cooker and including air control means normally operative to close and open the valve as the size temperature rises above and falls below a predetermined temperature, a timing device means for starting said device into operation at the beginning of a cooking operation, means actuated by said device after a predetermined operation 01' the latter to reduce the temperature at which said thermometer tends to maintain said size, means responsive to the temperature of the size in the, cooker and rendered operative on the attainment of a predetermined temperature lower than the first mentioned temperature to interrupt the operation of said timing device and to simultaneously render said thermometer inoperative to open said valve and to effect closure of the latter, and a second timing device rendering said last mentioned means inoperative at the end of a predetermined period or time following said temperature attainment.

close and open said valve as the size temperature rises above or falls below a predetermined temperature, air operated means forming part of said thermometer and operative when supplied with air to maintain the size at said predetermined temperature and when the supply 01' air is cut of! to maintain said sizeat a lower predetermined temperature, a supply oi air under pressure for said air operated means, valve means controlling said supply of air, a, timing device, means for starting said device in operation at the beginning or a cooking operation, and means operated after a predetermined extent of operation of the latter to actuate said valve means and cut oil the supply of air to said air operated means whereby the air operated means will act to maintain the size at said lower predetermined temperature.

- ANKER E. KROGH. 

